BRUCHID RESISTANCE OF COMMON BEAN LINES HAVING AN ALTERED SEED PROTEIN-COMPOSITION

Arcelin seed proteins of common bean (Phaseolus vulgar is L.) are toxi c to one of the most damaging pests of bean seeds, Zabrotes subfasciat us (Boheman), but they appear to have little effect on another importa nt bean pest, Acanthoscelides obtectus (Say), when introduced into sta ndard cultivars by backcrossing. With the goal of increasing arcelin c oncentration to improve resistance, we modified seed-protein compositi on by introducing a null allele for the major seed protein, phaseolin, into lines (SMARC1, 2 and 4) or three phytohemagglutinin types (SMPHA lines). These lines were tested for resistance to both insects by mea suring percentage insect emergence (%E) and days-to-adult emergence (D AE). For SMARC lines, arcelin type was the most important factor in re sistance levels, with SMARC1 lines being most resistant, SMARC2 lines intermediate. and SMARC4 lines the least resistant to both bruchids. A dditionally, the absence of phaseolin was a significant factor in the resistance of SMARC lines to A. obtectus. SMARC1 lines without phaseol in had half the percentage insect emergence of lines with phaseolin. S MARC1 lines with an altered seed composition had the highest levels of resistance to both bruchids of any large-seeded line reported to-date .